Hi Bob,
I agree that there are a lot of improperly set up radios and improperly set up
software programs on the bands! I operate mostly 6m and see that many people think
that they can just connect the cables and start operating FT8 :-( FT8 is most
certainly a very powerful innovation, and can lead to some amazing contacts. However,
FT8 is NOT "Plug and Play"!
Besides setting the audio levels properly for transmit, many users seem to have no
idea about audio harmonics or why the WSJT-X developers took so much effort to make
the program compatible with hundreds of different radios. This was not done without
purpose! This feature enables those radios to automatically shift frequency on
transmit, so the audio tones sent through the transmitter filter will not be
generating harmonics throughout the entire (typically) 2800 Hz transmitter filter
passband. An FT8 audio signal generated at 300 Hz will generate signals at 300, 600,
900, 1200, 1500, 1800, 2100, 2400 and 2700 Hz, and will become broader at each
harmonic. It doesn't take a rocket scientist to see that is pretty easy to completely
destroy the band by transmitting an FT8 signal using audio frequencies below 1500 Hz!
My suggestion to any newcomers to FT8 is the read the manual, and choose the proper
settings from the FILE/SETTINGS/RADIO screen so the transmitter frequency on your
particular radio will automatically shift as required when a different "offset
frequency" on the waterfall is selected for transmit.
If that cannot be understood or figured out, then the simple solution is to ALWAYS
KEEP YOUR TRANSMITTED AUDIO TONES ABOVE 1500 HZ BY SELECTING A TRANSMITTER OFFSET
ABOVE 1500 HZ! Simple as that.
Please share this information with anyone you see clogging up the bandpass with audio
harmonics. They probably are not aware of the problem and will be grateful for the
insights on how they can prevent generating QRM. It is the responsibility of everyone
to make sure that we educate everyone so the bands remain usable!
GL and VY 73, Lance
On 6/26/2022 19:26:35, Bob McGraw wrote:
------------------------------------------------------------------------
I operated FD from here at the house this weekend. Most all of my FT-8
contacts were on 6M.
I was appalled at the poor quality of many signals. Many show spurious
every 1 kHz to 2 kHz either side of their primary signal. Several were
noted to be bands of noise on the order of 2 kHz to 3 kHz wide. What
gives with hams and their pride for good quality signals? Bottom
line......this is poor operating and technical practice. Just because
it was Field Day, that is no excuse either. Have the masses digressed
to this level of non technical expertise? It sure seems so.
Then I was off to 80M and 40M for a few FT-8 contacts. No different.
WOW! This is all very disappointing.
73
Bob, K4TAX
--
Lance Collister, W7GJ(ex WA3GPL, WA1JXN, WA1JXN/C6A, ZF2OC/ZF8, E51SIX, 3D2LR,
5W0GJ, E6M, TX5K, KH8/W7GJ, V6M, T8GJ, VK9CGJ, VK9XGJ, C21GJ, CP1GJ, S79GJ,
TX7MB, TO7GJ)
P.O. Box 73
Frenchtown, MT 59834-0073
USA
TEL: (406) 626-5728
QTH: DN27ub
URL: http://www.bigskyspaces.com/w7gj
Skype: lanceW7GJ
2m DXCC #11 - 6m DXCC #815 - FFMA #7
Interested in 6m EME? Ask me about subscribing to the new Magic Band EME
email group, or just fill in the request box at the bottom of my web
page (above)!
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